1. Field of the Invention
The invention relates to a hydraulic element designed especially for assembling a drawing die with a blank holder and a shaping rim movable in relation to it, the hydraulic element being composed of working piston housed inside a working cylinder so as to be axially movable and so as to be acted on from the back by fluid pressure. The invention further relates to a drawing tool incorporating such a hydraulic element.
2. Discussion of the Prior Art
FRG-OS No. 34 24 262 discloses a drawing die having a drawing die cushion and composed of several pressure cylinders acted on by a hydraulic medium, with pistons being axially movable within the cylinders, for the support of a blank holder, and a further drawing die cushion holding a drawing punch movable in the drawing direction and having at least one pressure cylinder connected by passages to the pressure cylinders of the drawing die cushion supporting the blank holder and acted on by a hydraulic medium to be displaced relative to these pressure cylinders during the drawing operation, with a piston being disposed inside the pressure cylinder.
In the known drawing die, several additional pressure cylinders are thus assigned to a pressure cylinder supporting the movable drawing punch, and the blank holder that encloses the drawing punch rests on the pressure cylinders. It is characteristic here that during the downward travel of a drawing ring activated, for example, by an extrusion ram, the hydraulic medium escaping from the pressure cylinders of the drawing die cushion flows through suitable passages into the pressure cylinder of the further drawing die cushion and acts on a piston guided in the pressure cylinder, the piston in turn drives the drawing punch during the drawing operation in the drawing direction, opposite to the direction of travel of the drawing ring and consequently of the blank holder. This arrangement thus permits the execution of complex movements in opposite direction to the pull transmitted by the descending drawing ring and, similarly, the division of the desired drawing depth into partial drawings effected respectively by the descending drawing ring and by the ascending drawing punch.
In addition to these technical drawing possibilities there is a particular advantage to the known arrangement and also to the utilization of the pressure energy in the hydraulic medium displaced from the pressure cylinder supporting the blank holder by the downward travel of the drawing ring and the associated downward travel of the blank holder to drive the drawing punch in the direction opposite to the travel of the drawing ring.
The drawing technology made possible by this known arrangement has proven its usefulness. However, there is still need to improve the known arrangement with regard to simplicity and, above all, cost-effectiveness.